In 10 years in Brazil, Chikungunya reached 60% of cities – 04/09/2023 – Health

First identified in Tanzania in the 1950s, the chikungunya virus officially arrived in Brazil in 2013 – and caused the first outbreak in mid-2015 and 2016.

In a decade, the pathogen that is also transmitted by the bite of the aedes aegyptilike its “cousins” dengue and zika, spread to six out of ten Brazilian cities and caused seven major outbreaks.

These are some of the findings of an article that has just been published in the specialized journal The Lancet Microbe, signed by specialists from several national and international institutions.

Brazilian virologist William de Souza, one of the main authors of the work and a researcher at the World Reference Center for Emerging Viruses and Arboviruses at the University of Texas Medical Branch, in the United States, assesses that the impact of chikungunya on public health in the country has been somewhat widespread, in the midst of dengue and zika crises.

“Chikungunya was introduced in Brazil just one year before zika, the virus that caused that emergency because of the congenital diseases it causes in young children”, recalls the specialist.

“And dengue, in turn, has always been closely associated with severe cases and deaths.”

It is worth remembering that chikungunya infection has an acute phase, marked by fever, body pain and fatigue. However, in a number of patients, the disease progresses to the chronic form, marked by severe joint pain, which is disabling and can last for months.

The very name of the virus and the disease, by the way, comes from Makonde, one of the languages ​​spoken in Tanzania, where the first epidemic was recorded in 1953.

In this language, the word chikungunya refers to “writhe” or “bend”, in a direct reference to the strong discomforts that affect the joints and muscles and make patients curl up and prostrate.

“In general, people have the wrong idea that chikungunya causes pain, but does not kill”, observes Souza.

Therefore, in the midst of so many outbreaks and epidemics due to zika and dengue and an alleged low severity, chikungunya came to be seen as a matter of minor importance.

But the newly published study shows that the story is much more complex: in these ten years of circulation across the country, the virus caused seven outbreaks and had confirmed cases in practically 60% of Brazilian cities. It also affected women more than men — and had a higher death rate than previously thought.

pockets of cases

To carry out the research, the group of scientists gathered genomic and epidemiological data about the disease.

According to the study, between March 3, 2013 and June 4, 2022, 253,500 cases of chikungunya were confirmed in Brazil.

During this period, there were seven epidemic waves. They reached their peak in the first months of the year, mainly during the rainy season, and were repeated between 2016 and 2022.

These infections were confirmed in 3,316 of the country’s 5,570 municipalities, or 59.5% of cities.

And it is precisely here that the story begins to get even more detailed. The specialists decided to analyze in depth what happened in the most affected states: Ceará, Pernambuco and Tocantins.

They conducted a series of analyzes to understand why these locations concentrated the most cases.

In Ceará, for example, there were three major waves in 2016, 2017 and 2022.

“We know that chikungunya is a virus that can only be caught once. When a person has the infection, he develops immunity through cells and antibodies that most likely prevents a second episode of the disease”, says Souza.

This is different from what happens with dengue, which have four different types of the same virus – that is, a person can have this disease up to four times throughout their lives.

The team of academics even tested the hypothesis that there are new variants of chikungunya capable of reinfecting people – and, although they found different genotypes of the pathogen, they were not different enough to escape the defense cells and cause new episodes of the disease. in individuals who have had it in the past.

How then would a state have repeated outbreaks in a short period of time?

The answer lies in the geographic distribution of the outbreaks: in the case of Ceará, the cases in 2016 and 2017 were concentrated mainly in municipalities located further north.

Already in 2022, the epidemic wave happened in the cities further south.

You can see the difference in the map below — the stronger the colors that cities are painted, the higher the incidence of chikungunya cases in each location.

“Previously, we thought that chikungunya would arrive in a state, cause an explosion of cases and disappear”, analyzes Souza.

“However, unlike dengue, which spreads over larger regions, this virus affects smaller pockets in each outbreak”, he adds.

Greater impact on the female audience

Another finding of the study was that women are more affected by chikungunya compared to men, especially in adult life.

The risk of them testing positive for this disease is significantly higher compared to males.

Souza explains that the numbers of cases are relatively similar at the extremes of age – between children and the elderly.

The difference is apparent, as you can see in the graph in English below, between people aged 20 to 70 years. Women are represented by the color green and men, in the columns in blue.

In some age groups, women account for more than half of infections by this virus.

There are some hypotheses that help to understand this phenomenon. The main one has to do with human behavior.

“We know that dengue, zika and chikungunya infections happen mainly in the domestic environment”, contextualizes Souza.

“The configuration of society in many places in Brazil still follows that logic of the man going out to work while the woman takes care of the house and the children”, replies the virologist.

That is: as in many municipalities the adult woman remains more in the domestic environment than the man, she is naturally exposed for a longer time to the bites of the aedes aegypti that can carry chikungunya and other viruses

This thesis is supported by studies carried out abroad and also by the fact that children and the elderly of both sexes have a similar incidence of cases, since they tend to spend a similar amount of time indoors or out.

astonishing lethality

In previous works, in which Souza also participated, the team of scientists reached another relevant conclusion: that story that chikungunya does not kill does not correspond to reality either.

In an article published in 2021, the group reassessed 100 deaths that occurred in Ceará during the great wave that hit the state in 2017.

In all deaths, the main suspicion was arboviruses (diseases caused by a family of viruses that include dengue, zika and chikungunya).

Tests found chikungunya in 68 of the victims (or 52.9% of the total). In many of these individuals, the pathogen even caused damage to the central nervous system.

This allowed establishing a rate of 1.8 deaths per thousand cases of infection in that year, 2017, in Ceará.

“These are numbers that seem low, but when we have tens or hundreds of thousands of infections, they gain a very large scale”, points out Souza.

“In the period of this wave, it is possible to state that chikungunya caused more deaths than dengue in the region”, he compares.

“That is, the correct phrase to define this disease is ‘chikungunya causes a lot of pain – and can also kill'”, he adds.

Connection between statistics and real life

Doctor Claudia Marques, professor of rheumatology at the Federal University of Pernambuco (UFPE), saw in practice what was described in the recently published work.

She says that, at the height of the chikungunya crisis in Recife in 2016, the arrival of patients complaining of joint pain was a “very serious” scenario.

“At that time, people lined up at the hospital door. They were afflicted and couldn’t even walk properly”, reports the doctor, who was not involved in the research published in The Lancet Microbe.

“After that period, we no longer observe waves of cases around here. It’s as if the virus ‘exhausted’ one place and went to another”, reasons the specialist, who today receives reports similar to what she experienced in 2016 from fellow doctors who work in other cities, such as Salvador and Fortaleza.

“I can’t even remember the last time I treated a patient with rheumatic pain related to chikungunya around here”, says Marques, who is also the teaching and research manager at the Hospital das Clínicas at UFPE.

The doctor adds that, over time, health professionals themselves have been learning to deal with the chronic phase of chikungunya, when the pain lasts for more than three months and prevents the individual from carrying out daily activities.

“At first, we thought that most of those affected had an inflammatory condition and would need to deal with a type of arthritis for the rest of their lives”, he points out.

“Today we know that a minority will develop these inflammatory conditions, which require the use of immunosuppressive drugs.”

According to the rheumatologist, half of the infected patients have the acute condition of chikungunya, which lasts 14 days and then improves.

Of those who continue to have symptoms after these two weeks, about 30% progress to the chronic form, in which the discomfort lasts for three months or more.

“About 95% of these patients with the chronic form have non-inflammatory pain, which can be managed through stretching, physiotherapy and physical activity. Despite the long recovery time, which extends for up to two or three years, it is possible recover”, calculates Marques.

What to do?

Souza hopes that the research on the ten years of chikungunya in Brazil will inspire changes in public policies to contain the virus going forward.

After all, if cases of infection were confirmed in 60% of the municipalities in the last decade, this means that the pathogen can still spread and cause outbreaks in the other 40% that are free until now.

“Probably we will continue to see those epidemic waves in the coming years, which affect small pockets of municipalities within the States”, predicts the virologist.

“Our idea with this work was precisely to provide subsidies so that the government can determine which places are more susceptible”, he adds.

In other words, based on data analysis, city halls, state governments and even the Ministry of Health can concentrate prevention efforts, early diagnosis and treatment in those places that have not yet registered outbreaks (and are painted white or with colors clear on maps).

Another possible action, according to Souza, is to create public strategies to protect the most vulnerable, such as adult women. Since they are more affected, is it not possible to create an awareness campaign to control Aedes aegypti in the home environment aimed at this public?

By eliminating any reservoir of standing water – which serves as a breeding ground for the mosquito – it is possible to reduce the risk not only of chikungunya, but also of dengue and zika.

“Brazil is the country in the Americas most affected by chikungunya. In a scenario where we still don’t have medicine or vaccines available, we need public policies to prevent cases”, concludes the researcher.